This invention relates to a heat-sensitive record material and particularly to a heat-sensitive record material which has an improved heat-sensitivity and is adapted for a high speed recording so that it may find its usefulness as a recording medium for information machines and instruments such as facsimiles, electronic computers and telex machines.
There is known a heat-sensitive record material comprising a base sheet having a color developing layer which includes finely divided particles of one of colorless chromogenic materials such as triphenylmethane compounds, fluoran compounds auramine compounds and spiropyran compounds and finely divided particles of one of organic acceptors such as phenolic compounds, aromatic carboxylic acids and their polyvalent metal salt and/or one of inorganic acceptors such as activated clay, acid clay, attapulgite, aluminum silicate and talc. In such the heat sensitive record material like this the above mentioned two kinds of particles are, when at least one of them is melted or sublimated at an elevated temperature, brought into intimate contact with each other to develop a color. Accordingly, a relatively high temperature is required for obtaining clear and distinct color images. This is apparently disadvantageous since clear and distinct color images can never be expected at a high speed recording.
With an attempt to avoid the above mentioned disadvantages it has been proposed to disperse in the color developing layer a heat fusible material which can when melted, dissolve at least one of the colorless chromogenic material and the acceptor therein, e.g., as disclosed Japanese Patent Publication No. 4160 of 1968 and Japanese Kokai (Laid-Open) Patent Publication No. 19,231 of 1973. In this manner the heat sensitivity at low temperatures is improved. This improved system is useful for obtaining clear and distinct images if time for heating is relatively long as in case of the infrared copying. This system is not however utilizable for a high speed recording with such an extremely short heating time as 1 to 4 milliseconds which are required in high speed facsimiles since color can never be developed enough.
The primary object of the invention is to provide an improved heat-sensitive record material which can avoid the above mentioned disadvantages inherent with the conventional systems and can satisfactorily meet the requirements of recording machines and implements in which recording is carried out at a high speed and with a high image density.
Another object of the invention is to provide an improved heat-sensitive record materal which is immediately heat responsive and a good heat-sensitivity at low temperatures.
Other objects and advantages of the invention will be apparent from the following detailed description.